1. Field of the Invention
The present invention is directed to polyester polyols which have a low viscosity so that they may be formulated at high solids contents for use in the preparation of polyurethanes, particularly polyurethane coatings.
2. Description of the Prior Art
It is known to use polyester polyols for the production of hard, flexible polyurethane coatings having good acid and chemical resistance, gloss retention and abrasion resistance as well as light stability when (cyclo)aliphatic polyisocyanates are used as co-reactants. In order to obtain these properties highly branched polyester polyols are reacted with the organic polyisocyanates. However, due to the high degree of branching, the polyester polyols have a high viscosity and considerable amounts of solvent must be used to reduce the viscosity of the polyester polyols to an acceptable level, especially if the coatings are applied in a spray application. Because the use of large amounts of solvent may create environmental difficulties, particularly in a spray application, there is a need for polyester polyols which have a lower viscosity so that they may be formulated with less solvent than with previously known polyester polyols. It is also important to maintain the coatings properties obtained from the highly branched polyester polyols.
Accordingly, it is an object of the present invention to provide low viscosity polyester polyols which may be formulated at high solids contents than previously known polyester polyols such that the polyester polyols may be used in spray applications. It is also an object of the present invention to provide polyester polyols which may be used to produce polyurethane coatings which maintain the level of coatings properties obtained from the previously known polyester polyols, i.e. good acid and chemical resistance, gloss retention, abrasion resistance and light stability. Surprisingly, these objects may be achieved by using the polyester polyols of the present invention set forth hereinafter.